Re: A curiosity about decimal fixed point types...

[Oliver Kleinke <oliver.kleinke@c-01a.de>]

Am Mon, 11 Nov 2013 07:04:12 -0800 (PST)
schrieb mockturtle <framefritti@gmail.com>:

> Dear all,
> just a silly curiosity about decimal fixed point types, e.g.,
> 
>  type Euro is delta 0.01 digits 20;  
>  -- Would be 20 enough? :-)
> 
> Are they currently used? Where? Since most of the examples are about
> money (mine and RM's) included, I guess that they were thought for
> financial applications, but I am unsure if nowadays financial
> software uses this type of types or just floating point.
> 
> Best regards
> 
> Riccardo
> 

Hi Riccardo,

The type definition that you provided is a good example for using fixed
point types for accurate representation. With a fixed-point type you
can avoid the occasional precision problems that floating-point types
suffer from. (For example if I type "0.1 + 0.2" in my
Python-interpreter it yields 0.30000000000000004.)
This can be very important if you sum up/integrate a range of
measurement data obtained from a sensor -- for example a gyro.
Also, on some machines fixed-point arithmetic 'might' be faster than
floating-point arithmetic -- e.g. machines without FPU -- but I guess
that also very much depends on the operations and the compiler, &c.